Gas retaining fabrics and method of preparing the same



' Patented Apr. 14, 1936 -f2',0."','1,049f 7 goes RETAINING ,FABRIQSVAND METHOD or PREPARING THESAME In mar;sa e 'washmgtonjnuc. IN'o Drawing. Application October 4,1933,

,Se rialN0.692 ,22 6 g "-rolaims. (Chill-68) g '1 (Granted ,1tnantgae a March 3,1883, as

i g amended April 30, 1 928 ;,3700.:G; 757) 1 This invention relatesto gas retaining fabrics and a method .ofirendering 'such fabrics flexible and impermeable to fluids. 'Ihefgas retaining fabric hereinafter described is particularly adapt: ed for use in th'e'gas cells of airshipsalthough it is to be understood that it is applicable to other devices wherein a gas retaining or flexible fabric is desired;

An object of my invention is to provide a. fabric for the construction of gas cells have included gold-heaters skin, which is difiicult and expensiveto procure and to apply; rubber and various lacquers and varnishes, which either do not offer sufiicient resistance to diffusion of the inflating gases, or are not sufiiciently fiexibleto withstand severe flexing without cracking or checking.

The invention hereinafter described, which is intended to overcome the disadvantages of the fabrics heretofore employed, arises fromthe discovery that a film of polyvinyl alcohol is highly impermeable to hydrogen and in addition possesses a remarkable degree of flexibility and toughness.

In carrying out my invention an aqueous solution containing polyvinyl alcohol, obtained by hydrolysis of a low viscosity polyvinyl ester, such as polyvinyl acetate, is spread, brushed or sprayed upon a fabric, preferably a light, closely woven material, in a plurality of coatings. The fabric thus coated offers a very high resistance tothe difiusion of inflating gases, one fabric thus prepared having a total weight of coating of 1.8 ounces per square yard, indicating a permeability of one-tenth of a liter of hydrogen per square meter of surface within a periodof twenty-four hours. g

In carrying out my invention the spreading mixture may contain a plasticizer, such as glycerol, and a substance capable of combining with ture by means of a coating ofvarnis The proportions of the' various ingredients employed in the material maybe varied withinrelabrother. suitable proofing applied'toits surface. I

t'ively wide limits without departing from the 5 spirit of the invention. The following are examples of formulas which have been found to be satisfactory:

Example I Polyvinyl alcohol 30 grams Glycerol 7.5 do. Formaldehyde (40% aqueous solution)- 4 cc. Water 600 cc.

Exdmple II I Polyvinyl alcohol 40 gram Rubber latex (containing 30% solid matter) 200 do.

Glycerol 5 do. Formaldehyde (40% aqueous solution) 4 cc. Water 400 cc.

The solutions can be applied to a light weight, closely woven fabric by means of a spreading machine in a plurality of coatings. Each coat is 'I also provide a modified form of my improved coating in which the reaction product of polyvinyl and butyl aldehyde is the basis. In preparing this coating, I. dissolve one-hundred and fifty grams of polyvinyl alcohol in 1800 grams of water which has been heated to 70 0. Fifteen cubic centimeters of 36 percent hydrochloric acid are added and the solution stirred vigorously, the temperature being maintained at 65 to 75 'C. To this solution are added 96 grams of normal butyl al- 40 dehyde and the stirring is continued until the reaction product is precipitated as a rubbery mass.

This mass is removed and comminuted in cold water in an internal mixer, the water being replaced several times until the washed product is free'from acid. The product is pressed or centrifuged to remove excess water. The product, which may contain from to water, is

then dispersed in ethyl alcohol to form a viscous solution containing about 16% by weight of solid matter upon evaporation. To prepare a. reliable spreading mixture 25 grams of glycerol are added to 470 grams of the above solution and the mixture thoroughly stirred; The resulting coating can be applied to a fabric in a plurality I of coats, each coat being allowed to dry before the application of successive coats.

I desire it to be understood that various changes, including the varying of quantities and the percentages used, may be made within the scope of my invention. Thus, the reaction product of polyvinyl alcohol and butyll aldehyde and/or any aldehyde capable of rendering the coating insoluble in water may be dispersed in solvents other than alcohol, such as isopropyl alcohol,

imam methyl ether of ethylene lycoigethyia ether of ethylene glycol, and similar solve t Likewise, ethylene glycol, polyglycols and polyglycerols may be employed as softening agents in place of, orin addition to, glycerol.

From the foregoing description it will be apparent that l. have provided a new composition of matter to be utilized in the construction of gas cell fabrics for lighter-than-air craft. It'is'obvious that the examples enumerated serve merely as illustrations and that various modifications may be embodied thereinwithout departing from the spirit of the invention orfrom the scope of the appended claims.

V The invention herein described he manualcohol of a character and in suflicient quantity i to render the fabric impermeable to hydrogen.

2. A fabric capable of use in making gas cells,

product of polyvinyl alcohol, said reaction product containing polyvinyl alcohol of a character and in suflicient quantity to render the fabric impermeable to hydrogen.

3. A fabric coating comprising substantially rams polyvinylalcohol, 7.5 grams glycerol, 4 cc.

formaldehyde of a 40 percent aqueous solution, and 600 cc. water;

4. A fabric coating comprising substantially 40 grams polyvinyl alcohol, 200 grams of rubber latex containing 30 percent solid matter, 5 grams glycerol, 4 cc. formaldehyde of 40 percent aqueous solution, and cc. water.

; coated with a composition comprising a reaction ,THERON P. SAGER. 25 

